A technology for properly controlling a supercharging pressure of combustion air by adjusting a degree of opening of a wastegate valve provided on a bypass passage for exhaust gas in a supercharger (a supercharging system and a method for controlling the supercharging system) is disclosed in Patent Literature 1 below. In the supercharging system, a fully closed state of the wastegate valve (a fully closed position of a valve body) is corrected depending on a temperature of the supercharger, and thereby the degree of opening of the wastegate valve is properly adjusted regardless of the temperature of the supercharger.